This invention relates generally to the production of composite structures each produced by joining two or more separate materials to form a single unitary structure. More particularly the invention concerns the fabrication of composite structures by strongly joining a cladding plate to a substrate or base plate to obtain an integral structure. An example of such a cladding plate is made of aluminum or an alloy thereof. An example of the material for the base plate is steel. Examples of products which can be advantageously made of such composite structures are plate materials for tanks of liquid natural gas transport ships and reaction plates for linear motor vehicles.
More specifically, the invention relates to the production of anchor bonded composite structures each comprising a hard substrate or base plate made of a material such as steel and a relatively soft cladding plate made of a material such as an aluminum alloy and having a plurality of anchor parts which are forced under great pressing force into corresponding anchor cavities in the base plate, whereby the two plates are joined firmly to form a unitary structure.
An important feature of the invention is that, at the deepest portion of each anchor cavity in the base plate, one or more overhanging parts are formed, whereby, when the corresponding anchor part of the cladding is forced under great pressing force into this anchor cavity, the anchor part undergoes plastic deformation to assume a sectional shape of the letter T or Y in inverted from which completely fills the anchor cavity. Thus a positively locking joint or anchor bond is produced. A plural number of the anchor bonds of join the two plates as an integral structure.
A review of some aspects of the pertinent prior art may be instructive for an understanding of the present invention. As is known, laminated metal structures are becoming widely used as materials in various machines, devices, and structures. Examples, as mentioned hereinbefore, are reaction plates for linear motor cars and tank materials of liquid natural gas transport vessels. All required characteristics such as mechanical strength, corrosion resistance, behavior relative to heat, and elongation/contraction properties cannot be completely satisfied by a plate material of a single substance. Accordingly it is becoming a widely spreading practice to use plate materials produced by firmly joining base plates of hard steel and cladding plates of soft aluminum alloy to obtain an integral plate structure.
However, composite plate structures of the character described above have. heretofore been produced by methods such as explosion pressure bonding. The use of such methods is inconveniently limited by the dimensions of the product such as thickness. Furthermore, these methods require substantial labor, whereby production costs tend to rise.
Still another problem has been slippage at the interface between the two plates due to severe conditions of use such as vibration over a long period.